The present invention relates to a process and apparatus for coating workpieces, such as components to be used in industrial turbines and jet engines.
Components, such as vanes and blades, used in industrial turbines and jet engines are typically subjected to a coating operation to improve their resistance to corrosion, thermal fatigue, and to otherwise enhance their performance. Economic concerns dictate that one must be able to simultaneously coat multiple workpieces in order to have a viable commercial process and system.
A number of different systems have been developed to coat multiple workpieces at a single time using a modular fixture arrangement. Such systems are illustrated in published European patent application 953,656 to Burns et al., U.S. Pat. No. 5,997,947 to Burns et al., U.S. Pat. No. 5,849,359 to Burns et al., and U.S. Pat. No. 5,803,971 to Menchetti et al.
Certain coating techniques, such as electron beam physical vapor deposition (EB-PVD), are line of sight techniques wherein surfaces of a workpiece which are not in line of sight with the source of coating material will not be coated. It has been found that workpieces which are not kept at a constant distance from a source of coating material will have coatings which will later exhibit undesirable characteristics. This is particularly true for those workpieces which have an airfoil portion and surfaces requiring coating perpendicular to the airfoil portion.